From immune ascites fluid raised in a strain of mice syngeneic to the tumor cells we plan to isolate IgG1, IgG2a and IgG2b antitumor antibody. They will be compared for their effectiveness in suppressing the growth of the tumor, effector systems that cooperate with them in tumor suppression and their possible synergistic and antagonistic interactions with each other. The mechanisms of in vivo tumor suppression by purified syngeneic IgG1 antitumor antibody will be studied. In addition, the mechanisms of in vitro antibody dependent macrophage mediated tumor cell suppression will be studied at a biochemical level. BIBLIOGRAPHIC REFERENCES: Johnson, R., Pasternack, G. and Shin, H.S. (1977) Antibody-mediated suppression of tumor growth I. Suppression by murine IgG1 isolated from alloantiserum. J. Immunol. Accepted for publication. Johnson, R., Pasternack, G. and Shin, H.S. (1977) Antibody-mediated suppression of tumor growth II. Macrophage and platelet cooperation with murine IgG1 isolated from alloantiserum. J. Immunol. Accepted for publication.